2025PASP..137j4401L

Many potential direct imaging candidates suffer from large orbital period uncertainties, leading to challenges in accurate predictions of future orbital positions and imprecise direct imaging measurements of planetary parameters. To improve the precision in orbital properties, precursor radial velocity (RV) follow-up observations for selected candidates are essential. This study examines the impact of three variables on the orbital period uncertainties of long-period giant planets: the number of future observations, the temporal gap between past and future data, and the temporal coverage of upcoming observations. Our simulations indicate that the orbital phases at which future RV observations are acquired play a significant role in reducing period uncertainties. Additionally, observing too frequently within a given time frame adds limited value to the program once a certain number of observations has been achieved. The temporal gap proves to be the most important factor when there is no strict end time to the observing campaign. However, if a strict end time is set, starting observations earlier yields improved reductions in orbital period uncertainty. These insights offer practical guidance for planning efficient RV follow-up campaigns to maximize the science yield of future space-based direct imaging missions.